Causes
The occurrence and prevalence of melon disease must have three conditions in greenhouses and greenhouses: susceptible melon plants, a certain number of pathogens, and suitable environmental conditions such as temperature and humidity.
Pathogens. The presence of pathogens is a prerequisite for the onset of disease. The pathogens mainly include fungi, bacteria and viruses. These pathogens are attached to certain parasites or parasites, and are transmitted to the plants through certain channels when conditions are right.
The route of transmission is: 1 seed carrier. Seed carrier is the main way of disease transmission. Such as muskmelon bacterial leaf spot disease, anthrax, and other pathogenic bacteria can be overwintering or over the summer seed; 2 seedbed bacteria. Seedlings carry bacteria is the main route of transmission of seedlings. Seedbed soil from the cultivation of crops in melon crops or the application of organic fertilizer with pathogens but not decomposed, will make the seedbed bacteria; 3 seedlings carrier bacteria. When seedlings and plants are planted without strict selection and elimination of diseased seedlings, failure to inspect and remove diseased plants after planting will cause diseased seedlings to grow in the field, and then develop into a central disease strain; 4 diseased plant residues, weeds and Unripe organic fertilizer carrier. After melons are harvested, they are not picked up in time, and the remaining roots, pods, leaves, and fruits are not cleaned, buried or burned, and a large number of pathogens remain in the fields. Once the conditions are right, they will invade the plants; 5 soil carriers. In the greenhouses that have been replanted for many years, continuous crops, and greenhouses, the more pathogenic bacteria accumulate, the heavier the incidence and severity, so soil carriers are also important routes for transmission of melons; 6 Irrigation bacteria. The pathogenic bacteria contained in the water are generally washed out from the soil and pathogenic bacteria. Irrigation flow through the soil with bacteria, or diseased plant residues can spread disease; 7 insects carry bacteria. Is mainly sucking mouthparts of insects, such as the locust eating virus plants, and then smoking healthy plants will also spread the virus; 8 airborne bacteria. In the prosperous period of melon, the air contains a large number of pathogens, once the conditions are appropriate, it will be infected and the disease; 9 other. Greenhouses, greenhouse facilities, racks, agricultural implements, human bodies, etc. can also carry bacteria and spread diseases.
Suitable environmental conditions. The appropriate temperature and humidity are the main conditions for the onset of illness, especially the humidity. Because of the germination of most fungal spores, hyphae development requires higher humidity. For example, the occurrence of fusarium wilt, scab, and gray mold require the relative humidity of air to be above 90%, and the bacterial leaf spot disease, which requires lower humidity, should be more than 70%.
Causes of suitable humidity: 1 Continuous rain. Insufficient sunshine during rainy days, low temperature in sheds, poor ventilation, and high outdoor humidity, so the humidity in the shed is high, which creates conditions for the occurrence and prevalence of diseases. 2 release less wind. In greenhouses and greenhouses, the cold season has a short and short air release time for heat preservation, and the humidity in the greenhouse increases. 3 Insufficient bottom water or less cultivator results in more irrigation and more humidity in the field. Before planting or after planting, there is no pouring of bottom water; in addition, the panel will cause evaporation to increase and the soil loses water quickly, which will inevitably increase the number of watering and accelerate the occurrence and prevalence of diseases. 4 planting density is too large. However, the plants are not dense enough to cause poor ventilation, which makes the humidity in the shelter too large. 5 The quality of the site preparation is not high. The land is uneven, the surface is too large, the watering is not uniform, and the water in the low-lying area is easy to become the center of disease. 6 film dripping. When the temperature difference between the inside and outside of the greenhouse film is large, water droplets and water film are easily formed inside the greenhouse film. Where there is a lot of water, the soil is very humid and susceptible to disease.
Prevention
Reduce pathogens. 1 reduce the pathogeny of the seedbed. Avoid the use of old seedbed soil, use fertile soil, soil that has not been planted in melons for more than 3 years to make bed soil. Disinfection of bed land, fertilizer applied to seedbeds must be fully decomposed. 2 Prevent seed poisoning. Strengthen quarantine, try to transport seeds in a disease-free zone as far as possible, if the seed is disinfected by transporting seeds in the ward, methods include warm-soaking, seed dressing, and dry heat treatment. 3 to prevent diseased seedlings straight into the field. Before the colonization, careful examination should be conducted to eliminate sick and weak seedlings. A broad-spectrum fungicide was sprayed on the seedbed for prevention. 4 Implement rotation and pay attention to intercropping. A shed planting melon means not trying to grow other melon crops. 5 soil disinfection. Plunge 30 cm deep and dry. When the greenhouse is closed in summer, the temperature in the shed is raised, so that the surface temperature reaches 50°C-60°C. After 10-15 days of treatment, 50% of carbendazim 500 times is sprayed before planting. 6 shed disinfection. 10 to 15 days before sowing or planting, 1 to 1.5 kg of sulphur powder, 3 kg of sawdust, 5 to 6 points of iron on a piece of iron to ignite, or 250 g of 45% chlorothalonil smoke agent to ignite. Close the shed. 7 clean the pastoral. The weeds were removed timely during the growth of the melons, and the diseased leaves, fruits, and diseased plants were removed and brought out of the field to be buried or burned. After the melon has been pulled, clean up the debris in time or burn it.
Reduce humidity. Before planting, planting water should be poured after planting, and then the seedlings should be poured slowly and slowly. In case of watering during the growth period, small water should be drenched to cover the drip-free membrane; ridges should be used to cover the mulch; reasonably close-grained and cultivated with large and small rows for good ventilation; watering in the cold season should be conducted on a sunny morning.
Adjust the temperature. The incidence temperature of melon downy mildew is 22°C-22°C. Avoiding this temperature during cultivation can avoid the occurrence of diseases. For this reason, greenhouses and temperatures can be kept at a low temperature of 15°C-18°C during the night, and in the morning the temperature in greenhouses and greenhouses can be quickly increased to 25°C-28°C.
Cut off the source of infection. When working in the field, try to avoid cross-contact between diseased and healthy plants, pay attention to the prevention and control of locusts in time, and bring the sicknesses out of the fields.
Agricultural control. 1 Select resistant varieties. Such as Elizabeth, Taiwan Cuixiang. 2 Strengthen field management. To increase organic fertilizer, it is necessary to maintain adequate light, suitable temperature and humidity, timely pruning and harvesting when needed. 3 grafted. The use of black-skinned squash for sticky wood grafting can well control fusarium wilt. 4 top dressing. For dressing nutrients outside the root, such as using a mixture of sugar and urea (about 0.75 kg of sugar, 0.75 kg of urea, and 50 kg of water), spray once every 5-7 days to reduce the occurrence of downy mildew. Root dressing outside. 0.2% potassium dihydrogen phosphate also has the effect of preventing disease.
Chemical control. At the early stage of disease, the diseased plants should be controlled in time to control the occurrence of diseases. The use of pesticides is best for biological pesticides, followed by low toxicity and low residue pesticides. Such as the prevention and treatment of bacterial diseases should be used 72% of agricultural streptomycin sulfate aqueous solution 4000 times, 14% copper acid solution 200 times. The control of foliar diseases can be used for 45% chlorothalonil smoke, or 10% fast-kerose smoke, 250 g/mu, and 75% chlorothalonil or 70% manganese for sprayable pesticides. Zinc, 500-600 times liquid, 40% 200% aluminum phosphate aluminum, 200 times 2% agricultural resistance to resist 120, small Soviet Union to 500 times and so on. Prevention of virus disease in the early stage of disease virus A 500 times or 1.5% disease Lingshui emulsion 800-1000 times, 0.5% mushroom protein multi-Tang Shui agent 300 times, can also use silver plastic film or black plastic film to avoid Prevent disease.
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